1. Field of the Invention
The present invention relates to novel methods and systems for controlling the concentration of a component in a composition. The invention also relates to novel semiconductor processing methods and systems. The invention has particular applicability to the semiconductor manufacturing industry for online monitoring and control of the concentration of a corrosion inhibitor in a process chemical.
2. Description of the Related Art
Chemical mechanical planarization (CMP), also referred to as chemical mechanical polishing, and pre- and post-CMP storage and cleaning processes are commonly used in the manufacture of integrated circuits (ICs). To avoid corrosion of exposed metal during a metal CMP process, for example, for the planarization of copper-containing layers such as copper and copper-alloy layers, corrosion inhibitors such as benzotriazole, hydroquinone, tolyltriazole, imidazole, triazole, benzothiazole, mercaptobenzotriazole, gallic acid, pyragallol, catechol, recorsinol, etc., can be employed with the CMP slurry. In the CMP process, the corrosion inhibitor, typically in the form of a complex with the metal, passivates the metal surface of the wafer against chemical etching and allows uniform removal of the oxidized layer by mechanical action. The corrosion inhibitor complex also prevents the diffusion of oxygen into the wafer during subsequent, post-CMP cleaning operations. Liquid chemicals containing a corrosion inhibitor can also be used in a bath for storage or cleaning purposes before and/or after the CMP process to prevent corrosion of the metal surface.
It is desirable to maintain a known, constant concentration of the corrosion inhibitor in the CMP process and pre- and post-treatment baths in order to provide a manufacturable process. A decreased corrosion inhibitor level increases the likelihood of metal corrosion, whereas an increased concentration can result in corrosion inhibitor residue remaining on the wafer surface. These effects can result in a significant decrease in product yield. While off-line methods for measurement of the concentration of the corrosion inhibitors exist, such methods do not provide real-time feedback and control of the process.
Accordingly, there is a need in the art for methods and apparatuses for controlling the concentration of components such as a corrosion inhibitor in a CMP chemical and in pre- and post-CMP storage/treatment chemicals, which can provide real time, accurate process control in an easy and robust manner.